(1) Field of the Invention
The invention relates to electronic radiofrequency identification (RFID).
(2) Description of Related Art
For several tens of years, traceability data has been physically coupled to a component, e.g. in the form of an electronic tag that is itself physically attached to an article that is included in or that constitutes said component. The article or the component is said to be marked.
Applications are widespread and varied, from logistics to anti-theft marking, and including operational tracking of such articles or components.
One of the practical aspects of RFID identification is remotely writing/reading traceability data (or marking information) between a reader and the electronic tag. The term “contactless” is used as in “contactless” reading/writing, and “contactless” electronic device for structures such as the electronic tag.
At present, RFID identification faces two difficult technical problems when contactless reading/writing is to take place in a constraining environment.
The term “constraining” is used of an environment to cover two situations that may both occur simultaneously in certain applications.
For one of these two situations that define a constraining environment, reference may be made to the Wikipedia website using the search phrase “radio-identification”. It can be understood from that document that contactless reading/writing is “more difficult” for articles that are situated in a metal container. The potential communication distance is diminished by the Faraday cage effect, which performs electromagnetic shielding.
More generally, a constraining environment is an environment that forms undesirable electromagnetic shielding that serves to make contactless reading/writing difficult (i.e. possible at a short range close to making contact), or even impossible.
It is therefore conventional to seek to improve contactless reading/writing when the electronic RFID device is on a metal container. However there is no technical approach that is applicable in practice to certain specific circumstances when various environmental factors form such unwanted electromagnetic shielding.
In particular, in the proximity of contactless reading/writing spaces, these environmental factors forming electromagnetic shielding may comprise: metal and/or composite structures (on, in, and around the article or component to be marked); and the presence of interfering electromagnetic fields, e.g. due to the operation of computers, radars, and other electronic appliances.
Furthermore, the other technical problem of a constraining environment relates to so-called “extreme” operating factors of the external environment.
In particular, in the proximity of contactless reading/writing spaces, such extreme environmental operating factors comprise: temperatures that are high or low, e.g. of the order of −60° C./−30° C. to +150° C./+200° C.; high levels of humidity (lying in the range 0 to 100% relative humidity in air); and atmospheric pressure conditions (of the order of 500 hexapascals (HPa) to 10,130 HPa).
There are still other environmental factors that have a negative effect on contactless reading/writing: in particular factors that, over a longer or shorter length of time, are likely to give rise to deterioration of electronic devices or identification tags involved in such reading.
In examples of avionic identification systems in a constraining environment, a system needs to remain intact and functional under:
high temperature transitions (e.g. >95° C. per 20 minutes; and/or
impacts >15 grams per 20 milliseconds; and/or
vibration in the range 19.20 hertz (Hz)<NM×FM<28.70 Hz, according to document EUROCEA-ED14E-(DO160E)-Section—8: cf. the Radio Technical Commission for Aeronautics (RTCA) website.
It can be understood that when a plurality of these environmental factors are combined, contactless reading/writing and continued operation thereof are, at present, difficult if not impossible to maintain. This is problematic, in particular when contactless reading/writing needs to be guaranteed, in particular for safety reasons.
In order to illustrate how an environment can be constraining, the invention is described in its application to the field of managing the configuration of an aircraft for maintenance and logistics purposes in aviation, without the applications of the invention being limited to this particular example.
In this respect, mention is made of document FR 2 928 761 which describes the highly constraining environment within a helicopter in which tags need to communicate. The aircraft possesses structures that are intrinsic generators of radiofrequency interference, in particular because of its metal components, its fluid tanks, its connectors, and its on-board electronic equipment. On similar lines, the ambient operating conditions of electronic tags coupled with components of the aircraft are extremely aggressive, even though the lifetime of the components may be as much as 20 years or 6000 hours of operation, for example.
Furthermore, the standards and regulations in an aviation context are particularly strict, and the above-mentioned traceability systems must satisfy those requirements scrupulously.
Other documents may be mentioned that also distinguish the present invention. Thus, document “Antennas in our daily life, VII. The PIFA antennas.” (Aceli, 2004) describes a portable terminal with a plane and short-circuited curved antenna known as a planar inverted-F antenna (PIFA). A transmission face is connected to the electronics of the terminal, and a short-circuiting element is connected to a conductive grounding plane. Its performance can be improved by adding suitably placed fillers.
Document WO 2010/002542 describes an RFID device with a looped conductive antenna shield for near-field communication in the high frequency (HF) range. An electronic component is made to operate by using magnetic activity as opposed to electromagnetic activity as with UHF.
On the same lines, document “Orthogonally proximity-coupled patch antenna for passive RFID tag on metallic surfaces” (Hae-Won Son and Gil-Young Choi; ETRI; published on-line at the Interscience Wiley site under DOI10.1002/mop22222 on Aug. 8, 2006) describes several principles for tuning a chip with an antenna. An internal short-circuiting stud referred to as a “via” is placed inside a substrate perpendicular to its resonant length.
Document “Various UHF RFID tags for metallic object” (Yong-Kwon Park et al.; Daegu University; published on-line on the IEEE site under IEEE1-4244-0878-4/07—2007; pp. 2286-2288) describes passive tags having an antenna short-circuited by vias in the power supply line leading to the ground plane, and designed to be attached to a metallic article. A space is preferably provided between the antenna and the metallic article.
Document “Ceramic patch antenna using inductive coupled feed UHF RFID tag mountable on metallic objects” (Jeong-Seok Kim, et al. ILT-RFID Research Team; published on-line on the IEEE site under IEEE1-4244-2642-3/08—2008) describes UHF tags presenting a size of 25 millimeters (mm)×25 mm×3 mm and a short-circuiting plate on the edge face.
The document “Small RFID tag antenna to identify metallic objects” (Wonkyu Choi et al.; ETRI; published on-line on the IEEE site under IEEE978 1-4244-2042-3/08—2008) describes tags with two short-circuiting plates at corners of a ceramic substrate edge face perpendicular to a resonant direction.
Document GB 2 366 430 describes coupling an electronic RFID tag to a vehicle part in order to identify it and to deduce therefrom a technical procedure (specifically recycling) that is to be applied to the part after disassembly, as opposed to when it is incorporated in the vehicle.
Document US 2007/0241908 describes managing data relating to maintenance of an aircraft using electronic tags that are associated with components of the aircraft.
The transactions involved here generally take place in frequency bands lying in the range 100 megahertz (MHz) to 10 gigahertz (GHz), i.e. in the ultra-high frequency (UHF) range and the super-high frequency range (SHF).
At present, standards specify RFID interfaces in the field of marking articles as a function of the radiofrequency (RF) range used. Thus, the standard ISO18000-6 defines UHF communications parameters for an air interface in the range 860 MHz to 960 MHz. According to ETSI EN 302 208-1 V1.3.1 the radiofrequency regulations of that standard for the European geographical area specify a predefined maximum transmission power of 2 watts (W) effective radiated power (ERP). In the USA, it is the standard of the Federal Communications Commission, Title 47, Telecommunication, Chapter 1, Part 15-4-05-05 that is applicable, using a frequency in the range 902 MHz to 928 MHz, and according to Section 15.247 using a predefined maximum transmission power of 4 W effective isotropic radiated power (EIRP).
In practice, identification by means of (RFID/UHF) contactless reading/writing raises specific difficulties to which the above-mentioned documents do not provide a satisfactory solution.
Thus, present RFID identification techniques can give rise to safety problems. This applies for example if a damaged or read-silent tag leads to the maintenance or the replacement of a marked component or article to be avoided or performed late when it requires maintenance. The consequences can be catastrophic, since, in the event of such components/articles being critical elements, they have a bearing on the ability of an aircraft to fly.
Certain electronic tags have a range that is very short in a constraining environment (e.g. less than 100 mm to one meter). Consequently, the RF signals that are transmitted by such tags are sometimes not picked up (or are picked up incorrectly), thereby constituting a risk.
For example, with RFID reading/writing in an isolated theater of action with emergency action being taken while on campaign on a marked aircraft, a system of long-range on-board tags (typically active tags) goes against the safety constraints to which such an aircraft is subjected.
The weight of the traceability electronic systems including the tags coupled to the components in an aircraft are very penalizing, possibly preventing them being used.
Furthermore, the specific environment with which such tags need to communicate is very constraining, since an aircraft possesses structures that intrinsically generate radiofrequency interference, in particular because of its metal components, its fluid tanks, its connectors, and its on-board electronic equipment.
On the same lines, the ambient conditions in which the electronic tags coupled to components of the aircraft operate are extremely aggressive. Consequently, the lifetime of tags, in particular of active tags, runs the risk of not corresponding to the lifetime of the corresponding components that may be as much as 20 years or 6000 hours of operation, for example.
Furthermore, the standards and regulations in an aviation context are particularly strict, and the above-mentioned traceability systems need to comply with those recommendations scrupulously.
From the above, it can be understood firstly that increasing the range of on-board tags is not easy to achieve in practice.
Secondly, the use of tags that are lightweight and simple gives rise to reading problems (reliability, distances, etc.), to such an extent that at present it is not possible to envisage such tags being provided that do not have complex processors.